Field of the Invention
The invention relates to hoisting machines, and hoisting machine power supply. Particularly, the invention relates to an elevator line bridge filter for compensating reactive power in a grid.
Description of the Related Art
An elevator does work also when an elevator car is braked. The work done is usually lost as heat. The braking may be used to produce electrical power. Currently, the electrical power produced is not utilized.
In a power supply system loads may also have a combination of resistive, capacitive or inductive nature. Power may also flow towards the source. For example, electrical motors and lighting equipment have inductive coils which function as inductive load. The power caused by inductive or capacitive loads is referred to as reactive power. When reactive power is present, there is a phase difference between voltage and current. Reactive power causes rise in current value in the internal grid of the building and therefore causes heating in power transmission lines and all kinds of power supply lines of the building.
A building automation system controls a plurality of electricity consuming subsystems in a building. The building automation system monitors and controls several subsystems of the building such as lighting, heating, air-conditioning and security. A building automation system comprises at least one computer, which is referred to as a building automation server. The server is connected to a plurality of sensors that monitor the proper functioning of the aforementioned subsystems. The building automation system may also measure use of electrical power in the aforementioned subsystems. Some of the aforementioned subsystems may have reactive or inductive loads which give rise to reactive power, which returns to the power source such as a grid unless it compensated. The building automation system may also measure reactive power.
Therefore, it would be beneficial to have a solution which enables a building automation system to perform compensation for reactive power. It would be beneficial if an elevator system was able to compensate reactive power produced by a plurality of building subsystems.